Adjustable sound level control for audible signals of the vibratory type



Feb. 24, 1959 2,875,433

R'. D. BEA ADJUSTABLE SOUND LEVEL CONTROL FOR AUDIBLE SIGNALS OF THE VIBRATORY TYPE Filed Dec. 27,1956 2 Sheets-Sheet 1 INVENTOR. I Roscoe D. Bean ATTORNEYS R. D. BEAN D L Feb. 24, 1959 2,875,433

ADJUSTABLE SOUN EVEL CONTROL FOR AUDIBLE SIGNALS OF THE. VIBRATORY TYPE 2 Sheets-Sheet '2 Filed Dec. 27, 1956 INVENTOR. I Roscoe D. Benn ATTORNEYS ADJUSTABLE SOUND LEVEL CONTROL FOR SIGNALS OF THE VIBRATORY Roscoe D. Bean, Shrewsbury, N. J., assignor to Wheelock ignals, Inc., Long Branch, N. J., a corporation of New ersey Application December 27, 1956, Serial No. 630,793 5 Claims. (Cl. 340-392) This invention relates to bells and more particularly to electromagnetically actuated bells incorporating sound intensity control means.

One widely used technique for controlling the intensity of the sound which radiates from a bell shell engaged by a vibrating striker is to adjust the relative spacing between the bell shell and the mean or neutral position of the striker. This technique, which is used in many telephone bell installations, can be simply effected by a screw adjustment which shifts the bell shell in lateral translation relative to the electromagnetic striker motor. While this efiectively changes the intensity of the sound emanating from the bell shell, it also results in an undesirable change in quality of the sound. Moving the bell shell closer to the striker, for example, tends to produce a somewhat muddied ringing tone of lower intensity.

In accordance with the present invention, therefore, there is provided a bell assembly including a bell shell, a striker, and an electromagnetic motor for driving the striker into the bell shell in a vibratory ringing pattern, with means being provided for effecting a range of adjustments of ringing intensity in which the tone or quality of the sound is maintained at a uniformly high level over a considerable range of sound intensities. To this end, the striker, which can take the form of a vibratory plunger in an electromagnetic solenoid-type system, can be positioned relative to the bell shell so that a fixed distance obtains between the mean or neutral position of the striker and that part of the bell shell The electromagnetic drive is such which it engages. that the striker moves on either side of the neutral position, engaging theb ell shell on one side and selectively engaging an adjustable abutment on the other. adjustable abutment is movable relative to the neutral position of the striker, and hence to the bell shell, to control the amplitude of the travel of the striker, not between the neutral position and the bell shell but between the neutral position and the most remote position thereof. 9

This adjustment can be effected in accordance with the present invention by providing an abutment shoulder on the striker, preferably of resilient material, which engages an adjustable abutment carried by the frame of the electromagnetic motor. The adjustable abutment is selectively movable toward or away from the shoulder to control the travel of the striker away from the bell shell. In the event the electromagnetic motor is of the polarized, tuned resonant type, for example, maximum ringing intensity can be effected by shifting the abutment fully out of the path of travel of the shoulder which moves with the striker. Moving the abutment into the outer range of movement of the shoulder first acts to alter slightly the resonant conditions so that the striker energy is reduced, and secondly serves to limit the stroke of the striker from its outermost position to the bell shell. Surprisingly, both of these factors have been found to The 2,875,433 Patented Feb. 24, 1959 decrease the sound intensity, with very little influence on the tone or quality of the sound.

A representative embodiment of the invention from which the above and other features thereof will be readily apparent is described below, having reference to the accompanying drawings in which:

Figure l is a view in rear elevation of a bell assembly Referring to the drawings, the invention is illustrated.

as embodied in a bell assembly 10 which is of the continuously ringing type in which the striker tip 11 engages the bell shell 12 a number of times per second, say sixty. The bell shell 12 is fixed to a supporting frame, indicated generally bythe numeral 13, as by a central mounting bolt 14, for example, with the frame 13 also carrying, preferably within the hollow of the bell shell 12, an electromagnetic motor, indicated generally by the numeral 15, for driving the striker tip. The electromagnetic motor 15 can be formed, for example, in accordance with the disclosure of the patent to Werner, No. 2,708,245, the motor including a generally U-shaped frame 16 formed with a pair of mounting slots 17 and 18 in its back portion 19, and a pair of integrally formed parallel arms 20 and 21, all of ferromagnetic material. The arms 20 and 21 embrace a permanent magnet 22 and a coil or winding 23 formed with aligned central apertures 22a.

and 23:: through which passes a non-magnetic core sleeve 24, the opposite ends of which enter and are secured in holes 20a and 21a in the arms 2b and 21.

Freely slidably mounted in the sleeve 24 is a plunger 25 formed of magnetic material and having afiixed to its outer endthe striker tip 11, which is non-magnetic. When the coil 23 is energized through the electrical conduit 26 from a suitable source of alternating current, the plunger 25 will be driven back and forth with magnetically powdered strokes in each direction at the frequencyof the energizing source. If desired, in order to tune the vibrating frequency of the plunger 25 to establish a natural resonant frequency which matches that of the energizing source, a tuning spring 27 can be coupled between a lug 28 on the inner end of the plunger l and a bracket 29 secured to the frame arm 21. Preferably, the spring 27 and bracket 29 are formed of nonmagnetic materiali In operation, the spring does not operate as a return spring for driving the plunger in one direction, but is' simply a tuning spring which can be used to increase ringing intensity.

critical in the sense that the maximum intensity of sound emanating from the bell shell, as well as the highest quality tone obtainable therefrom, are achieved through this adjustment. In certain adjustable intensity bells used heretofore, this distance has been selectively variable tovarythe sound intensity. As stated above, how

ever, adjustment of sound intensity in this fashion also results in a certain undesirable change in the quality of the sound, the bell tones becoming more muflled in character as the sound intensity diminishes. For maximum clarity of sound, as well as for maximum sound intensity,

. 3 there isusually but onespacingbetween the striker tip 11 and the bell shell, and it is this spacing which is achieved and preferably permanently fixed at the time of manufacture.

In accordance with the present invention, in order to vary the intensity of the sound, sound intensity adjusting means 34 is provided for changing the travel of the strikformed in the plate 38. A polygonal nut 41 is threaded onto the stud 39, and the plate 38 is forced upwardly against the nut by a compression spring 42, preferably carrying a dished washer 43 in its upper end. The inner end' of the plate 38 is forced outwardly against the upper edge of the opening 36 in the bracket 35 by a second compression spring 44. The striker tip 11 passes outwardly through the keyhole opening 40 in the plate 38 and, beyond the plate, carries a shoulder 45 which can include, on its surface facing the plate, a resilient covering 46. The plate 38 is formed with a pair of parallel upstanding lugs 47 and 48 adjacent the narrow end of the keyhole opening 40 to embrace the inner end of the nut 41 so that the nut is constrained against turning movement.

To adjust the spacing 49 between the inner surface of j the resilient cover 46 and the abutment plate 38, the plate 38 is pivoted inwardly toward the arm 20 to free the.

at which time the plate is released to lock the nut in position. Also, it will be seen that the abutment plate 38 can be readily mounted in its operative position at thetime of assembly of the unit by first passing the plate downwardly over the shoulder 45 using the large end of the keyhole opening. The slotted end 37 of the plate is then pushed into the large portion of the stepped opening 36 and released to allow the spring 44 to force it against the outer end of the opening, with the slots engaging the constricted wall of the bracket 35.

In operation, when it is desired to achieve the maximum sound intensity from the bell shell, the abutment plate 38 is screwed inwardly so that the shoulder 45 does not engage it at any time. The plunger 25 is then free to reciprocate under resonant conditions to cause the striker'tip 11 to engage the bell shell withmaximum force. Adjusting the nut 41 outwardly on the stud 39 brings the abutment plate 38 into the outer fringes of the; path of-travel of the shoulder 45. This slightly impairs the tuned resonant action of t the plunger, which slightly decreases the intensity of the sound due to the decreased energy of its stroke. the plate38 bringing it further into the field of travel of the. shoulder further upsets resonant conditions and, moreover, begins to significantly limit the total travel of the plunger from its position most remote from the bell shell to the neutral position. The total kinetic energy of thestriker tip is thereforereduced. At no time, how: ever, is-the distance between the neutral position of the plunger and the bell shell altered, so that, surprisingly, the

quality offthesound is not changed significantly.

While the invention has beendescribed above with referenceto one particular type of-electromagnetic motor having a reciprocating plunger, i. e., a motor in which electromagnetic force is imparted for both the in and.

. that disclosed in Patent No. 2,561,355, can be used in Further adjustment of:

which magnetic action drives the plunger-in one directionand a spring drives it in the other. Also, if desired, a tubular resonator 50, formed with an opening 51 next to the bell shell at the point of engagement of the striker, can be provided to enhance the ringing sound. The resonator St is carried by arms 52 and 53 attached to t he frame 13. The invention should-not, therefore, be regarded aslimited, except as defined in the following claims.

I claim:

1. In an electrically actuated bell assembly having a ringing action of adjustable intensity, a bell shell, an electromagnetically actuated motor including a. reciprocating armature movable to and fro across a mean'position, striker means movable with the. armature to engage the bell shell in continuous ringing action upon energization of the motor, support means to mount the bell Shell and motor in relatively fixed relationship with a predetermined, fixed spacing between the mean posi-. tion of the armature and the striker means and the bell shell, adjustable abutment means selectively interposeble to block the travel of the armature from its mean position to its position in which the striker means is remote from the bell shell, thereby to vary the intensity of the ringing action, said abutment means, including a shoulder carried by the armature intermediate the striker means and the motor, and a spring supported plate adjustable with respect to the support means along the path of travel of said shoulder, said plate serving as a yieldable and adjustable stop for the shoulder.

2. In an electrically actuated bell assembly having a ture at substantially one extreme position of its travel,

support means to mount the bell shell and motor in relatively fixed relationship with a predetermined fixed spacing between the mean position of the armature and the bell shell, adjustable abutment means selectively interposable to block the path of travel of the armature from its mean position to its position in which the striker is remote from the bell shell, thereby to vary the intensity of the ringing action, said abutment means including first shoulder means carried by the armature .and second shoulder means adjustably movable in the direction of travel thereof, said second shoulder means comprising an apertured plate member through which the armature passes, and means to adjust the relativeposition'of said first and second shoulder means.

3. A bell assembly as set forth in claim 2, said plate being movably mounted, spring means urging the plate in the direction of the first shoulder means, and screw means to fix the position of the plate member against the'force of said spring means.

4. A bell assembly having a ringing action of adjustable intensity with substantially uniform energizing: signals comprising a bell shell, an electromagnetic motor including an assembly of a coil, a permanent magnet,

a ferromagnetic frame and'an armature, the armature being mounted in the assembly for free axial recipro catory motion to and fro across a mean position when the coil is energized with an A. C. signal, striker means on one end of the armature to engage the bell shell, a

common support for the motor and shell establishing a predetermined fixed distance between the shell and the mean position of the armature and striker means, an adjustable abutment selectively interposable to block the of the ringing action, said adjustable abutment means comprising a shoulder on the armature and an apertured plate member carried by the common support, said armature passing through the aperture in the plate member, a spring urging the plate member in the direction of the shoulder on the armature, and screw means to hold the plate adjustably in position against the action of the springs and thereby determine the relative spacing between the shoulder and the plate member.

5. In an electrically actuated bell assembly having a. ringing action of adjustable intensity, a bell shell, a motor including a reciprocating armature, striker means movable with the armature of engage the bell shell upon energization of the motor, support means to mount the bell shell and motor in relatively fixed relationship with a predetermined fixed spacing between the mean position of the armature and the bell shell, an extensible spring connecting the end of the armature remote from the striker means and said support means, means freely accessible for adjusting the length of said spring, a shoulder carried by the armature intermediate the striker means and the motor, and a stop adjustable with re spect to the support means along the path of travel of the shoulder, said stop being adjustable to limit the travel of the armature from its mean position to its position in which the striker means is remote from the bell 10 shell, thereby to vary the intensity of the ringing action.

References Cited in the file of this patent UNITED STATES PATENTS Bossard Mar. 28, 1939 

